This invention relates to a hydrometallurgical process for extracting copper from ore containing oxidized and sulfidic copper minerals by the utilization of an acidic ferric sulfate solution and the continual regeneration of the ferric sulfate solution to permit a cyclic system. The system is of high efficiency and low energy consumption.
Solutions of acidic ferric sulfate have been used to vat leach copper values from sulfidic copper-containing minerals. The chemistry and practice of such leaching are well established. With sulfidic ores only ferric sulfate need be used and the reaction, using covellite for purposes of illustration, is as follows: EQU CuS+ Fe.sub.2 (SO.sub.4).sub.3 .fwdarw. CuSO.sub.4 + 2FeSO.sub.4 + S.degree.
when oxidized and sulfide minerals are associated together in the ore, the leaching solution contains both sulfuric acid and the ferric sulfate, the sulfuric acid being necessary to dissolve the oxidized minerals. In both instances, however, the ferric ion is reduced to ferrous ion, and prior proposals to reoxidize the iron to the ferric state to utilize the sulfate solution for leaching of additional ore have the disadvantage of being costly or uncertain.
In the past, such reoxidation has been effected in an electrolytic facility with simultaneous deposition of copper within the same electrolytic circuit. Such simultaneous actions sacrifice the individual efficiency of each reaction; but, even if the regeneration of the iron to the ferric state is alone carried out, the operating costs are very large.
It is also known that ferric iron can be regenerated by exposure of the leach solution, after separation of the copper (e.g. by cementation), to air. However, adequate build-up of ferric iron in the solution by this procedure is not always successful.